Ventilation valve for closing a ventilation duct in a casting mold

ABSTRACT

A ventilation valve for closing a ventilation duct in a casting mold, the valve comprising a valve cylinder; a valve piston slidingly received by the valve cylinder so as to be movable between an open and a closed position in a direction perpendicular with respect to said ventilation duct, said valve closing in the direction of the pressure exerted onto the surface of said piston which faces said ventilation duct, a displacement member which urges the piston into its open position when the mold is open; and means actuated by closure of the mold to move the displacement member away from the piston so that the piston can be brought to its closed position without being hindered by the displacement member load.

[451 May 27, 1975 VENTILATION VALVE FOR CLOSING A VENTILATION DUCT IN A CASTING MOLD [76] Inventor: Fritz Hodler, 28, Ave. de Collonge,

Territet, Switzerland [22] Filed: June 25, 1973 [21] App]. No.: 373,128

[30] Foreign Application Priority Data Oct. 5, 1972 Switzerland 14572/72 [52] U.S. Cl. 164/305; 164/410; 425/812 [51] Int. Cl B22d 17/20 [58] Field of Search 164/305, 410; 425/420, 425/812 [56] References Cited UNITED STATES PATENTS 2,867,869 l/1959 I-Iodler 164/305 X 2,976,568 3/1961 Foti 425/812 X 3,349,833 10/1967 l-Iodler 164/305 X 3,433,291 3/1969 I-lodler 164/305 FOREIGN PATENTS OR APPLICATIONS 306,274 3/1955 Switzerland 1,483,579 10/1969 Germany [64/410 Primary Examiner-Robert D. Baldwin Assistant Examiner-John E. Roethel Attorney, Agent, or Firml-lill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57} ABSTRACT A ventilation valve for closing a ventilation duct in a casting mold, the valve comprising a valve cylinder; a valve piston slidingly received by the valve cylinder so as to be movable between an open and a closed position in a direction perpendicular with respect to said ventilation duct, said valve closing in the direction of the pressure exerted onto the surface of said piston which faces said ventilation duct, a displacement member which urges the piston into its open position when the mold is open; and means actuated by closure of the mold to move the displacement member away from the piston so that the piston can be brought to its closed position without being hindered by the displacement member load.

17 Claims, 4 Drawing Figures VENTILATION VALVE FOR CLOSING A VENTILATION DUCT IN A' CASTING MOLD The present invention relates to a ventilation valve for closing a ventilation du ct in a casting mold, the valve comprising a valve cylinder; a valve piston slidingly received by the valve cylinder so as to be movable between an open and a closed position in a direction perpendicular with respect to said ventilation duct, said valve closing in the direction of the pressure exerted onto the surface of said piston which faces said ventilation duct, a displacement member which urges the piston into its open position when the mold is open; and means actuated by closure of the mold to move the displacement member away from the piston so that the piston can be brought to its closed position without being hindered by the displacement member load.

Ventilation valves of this type, which compared with those which close in the opposite direction (German Pat. Nos. 1,044,364 and l,458,l36) have the considerable advantage that it is not necessary to apply any particularly high energy to keep them closed when the casting material reaches the valve, since the pressure of the casting material which flows thereafter is sufficient in itself to achieve this. In the case of known ventilation valves which close against this pressure, it is necessary on the other hand to provide a closure pressure of 100 to 150 kg/cm Ventilation valves may not be selected to be of any desired size in order to achieve actuation of the valve piston with a fairly low specific pressure, as, in the case of most casting molds, as a result of the core pressures frequently applied on all sides, there is only very little space available for the introduction or removal of a ventilation valve. The afore-mentioned high pressures which are generally applied by means of hydraulic pressure means lead, however, to expensive, rapidly wearing seals and to a considerable risk of accident, principally because of the possibility that the pressure medium may escape and come into contact with molten metal in the melting pot near the casting machine, and cause explosions.

In addition there is the disadvantage in the case of most of the known ventilation valves that they are not sufficiently reliable in operation. The valve piston is housed in a lateral wall of the ventilation duct, and to achieve closing its front face is pressed against the opposite-facing duct wall, and this means that fins may succeed in adhering to the front face of the piston, these occurring as the result of the hardening of liquid casting material forced between the piston and the duct wall which acts as a valve seat. These fins" are difficult to remove in most cases and therefore render impossible satisfactory operation of the valve. It is not even possible to avoid the formation of these when using maximum closure force, as the opening speed of the two halves of the casting mold is greater, in the event of the spurting of the casting mold caused by the pressure amplitude of the casting material, than the closure speed of the piston of the ventilation valve.

The formation of fins which have a disadvantageous effect on their operation is, however, not removed even in the case of known ventilation valves of the type referred to initially, as these valves have a steplike valve seat in the valve cylinder on which the valve body rests during closure in order to provide sealing (Swiss Pat. No. 306,274). The fins may occur between the valve seat and the valve piston and also between the cylindrical walls of the piston and cylinder and therefore give rise in some cases to incomplete closure or to jamming of the piston in the valve cylinder.

Attempts have already been made to reduce the force necessary to close the ventilation valves by providing a ventilation valve lateral to the ventilation duct, with a valve piston adapted to move parallel to the length of the duct and the lateral inlet and outlet members. In this case the valve piston closes perpendicularly to the direction of the pressure of the casting material acting thereupon when the valve is closed (German Pat. No. 1,483,579). This ventilation valve has proven itself particularly wherever the operatives have a continuous visual control over the valve, which in most cases is located at the plane of separation of the casting mold, and are therefore able to immediately remove small fins forming in the direct vicinity of the valve inlet. However, visual control is no longer possible with the large casting molds used in many cases today. If under such circumstances a fin on the outside of the valve cylinder is not removed, then, when the mold is closed, it exerts via the small fin an enormous local surface pressurevof in many cases over 10,000 kg/cm on the wall of the valve cylinder, this generally leading to deformation or buckling of the inner wall of the valve cylinder against which the valve piston is adjacent. This can in turn lead to the piston jamming as, for reasons of sealing, the piston may only have an extraordinarily small play relative to the cylinder wall.

The object forming the basis of the invention is therefore to facilitate, in the case of a ventilation valve of the type referred to above, re-opening of the valve without the use of high-pressure pneumatic or hydraulic pressure media even if its piston has jammed in the cylinder as a result of fins which have penetrated between it and the cylinder wall or as the result of the influence of temperature, while bearing in mind that when the mold is closed the valve piston remains in an unstressed condition until its control force acts, so that it is possible to close the ventilation duct with only slight pressure force and in the shortest time possible.

The presentinvention provides a ventilation valve for closing a ventilation duct in a casting mold, the valve comprising a valve cylinder; a valve piston slidingly received by the valve cylinder so as to be movable between an open and a closed position in a direction perpendicular with respect to said ventilation duct, said valve closing in the direction of the pressure exerted onto the surface of said piston which faces said ventilation duct, a displacement member which urges the piston into its open position when the mold is open; and means actuated by closure of the mold to move the displacement member away from the piston so that the piston can be brought to its closed position without being hindered by the displacement member load.

This means that the valve may be re-opened with reliability, even if its piston is jammed as the result of fins or the influences of temperature, in which case the piston is completely relieved of stress when the mold is closed.

It is expedient if the valve piston is designed as a plunger piston with a sealing piston head and, when housed in a valve cylinder without a valve seat, closes exclusively by means of plunging. In this event it should enter into the valve cylinder to such an extent that its front face, which faces the ventilation duct, is located just inside the bore of the valve cylinder. This means that there is the certainty of avoiding the formation of fins which would otherwise form at the edge of the valve inlet if the latter has been slightly damaged.

The impact surface, adapted to be impinged upon by casting material, of the valve head protruding against the cylinder wall of the valve is, in the case of the ventilation valve according to the invention, preferably sectioned in such a way that it protrudes with its radially outer edge in axial alignment of the valve piston against the direction of pressure of the casting material. This means that the casting material exercises such a pressure on the radial protrusion of the valve head that the protrusion is pressed in a sealing manner against the cylinder wall with its lateral edge lying back in the direction of closure of the valve. It is further expedient in this context if the peripheral wall of the radial protrusion is slightly inclined at the piston head relative to the inner wall of the valve cylinder in such a way that it gradually increases its distance from this cylinder wall in the direction of closure. The pressing of the radial protrusion of the piston head may be made easier or improved further if the radial protrusion has at or near its foot such a narrow cross-section width that it is possible to bend the radial protrusion against the cylinder wall in this area in the event of casting material pressure acting on the front surface of the valve piston.

The invention will be described further, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is an axial section through a ventilation valve housed in a casting mold, the mold being in the open position;

FIG. 2 is a view similar to FIG. 1, the valve being open and the casting mold being in the closed position;

FIG. 3 is an axial section on an enlarged scale in partial section of the valve head of the closure valve shown in FIGS. 1 and 2; and

FIG. 4 is an axial section through a second embodiment of the closure valve in the closed position with the casting mold in the closed position.

In the casting mold shown in FIGS. 1 and 2 one half 1 of the casting mold has a recess for the reception of the valve cylinder 3 of a ventilation valve, while the other half 2 of the mold contains a ventilation duct 4 adjacent to the plane of separation of this mold. The ventilation duct 4 opens into a pressure distributing area formed in the half 2 of the mold, opposite which lies the valve inlet 16 in the valve cylinder 3, this inlet having a somewhat smaller cross-section; the inlet 16 leads into the cylinder bore 17 which slidably receives the valve piston 5.

Behind its piston head 6, which protrudes radially towards the cylinder bore 17 to achieve sealing, the piston 5 has a narrow zone forming with the wall of the cylinder bore 17, a passage 18 for the air which escapes or is to be compressed out of the mold from the mold cavity via the ventilation duct 4. In the narrow zone the valve piston 5 has peripheral guide projections 7 so that it may slide with its piston head 6 with high accuracy in the bore 17 of the valve cylinder 3.

The valve piston 5 is designed as a plunger piston which closes exclusively by the entry of its head 6 into the cylinder bore 17. Thus a step-like valve seat at the inner wall of the bore 17 is superfluous, which seat would lead to the formation and collection of fins between piston and cylinder and render trouble-free working of the valve impossible.

At the end remote-from the valve inlet 16 the valve piston 5 has a piston plate 12 with a substantially greater diameter guided sealingly in a widened part of the cylinder bore 17. When the mold is open (FIG. 1) this piston plate 12 is pressed to the left (FIG. 1) towards a bearing surface 20 for the piston plate 12 (via mobile stops 19) by a displacement member 9 which is similarly guided in sliding manner in the widened section of the cylinder bore 17. This pressure is achieved by means of plate springs 10, which are compressed between the displacement member 9 and a bolt 11 forming the base of the valve body 3 which attempt to press the displacement member 9 towards the valve piston. The initial stressing of the plate springs 10 is by screwing of the bolt into the valve cylinder to a suitable extent. In order to achieve accurate guiding of the displacement member 9 in the valve cylinder 3, use is further made of a guide shaft 21 coaxially with it on which the plate springs are placed and which engages slidingly in a blind bore 22 of the bolt 11. The depth of this blind bore is at least equal to the stroke height h necessary to close the valve.

In order to actuate the ventilation valve, when the mold is closed (FIG. 2), it is possible to introduce, via a connection 13, a pneumatic or hydraulic pressure medium into cylinder region 23 which is located to the left of the piston plate 12 in FIG. 2 of the drawing, as a result of which the valve head 6 enters the cylinder bore 17, and the connection between ventilation duct 4 and the outlet 14 of the ventilation valve is interrupted; the outlet 14 may lead to an evacuation system or into the free atmosphere.

The stops 19 located between the piston plate 12 and the displacement member 9 are seated at the end of stress-relieving rods 8 which pass through the piston plate and the wall of the valve cylinder 3, and are longitudinally displaceable. When the mold is open (FIG. 1) the springs 10 press the valve body 5 (through the displacement member 9, stops 19, and piston plate 12) to the left into its open position, in which the piston plate 12 lies against the valve seat 20. In such a case the rods 8 are similarly moved in their bores in the valve cylinder, to the left into the position shown in FIG. 1. Their length is such that in this position they project from the valve cylinder 3 by at least the stroke height of the valve piston 5 necessary to close the valve.

As the mold is closed the rods 8 are displaced to the right against the force of the springs 10 (FIG. 2) thus displacing the piston 9 by means of the stops l9 and once again subjecting the compression springs 10 to the initial stress. The valve piston 5, which is not solidly connected to the rods 8 or their stops 19, remains in the open position, however. It is as a result no longer subject to any pressure loading of any kind and in the subsequent casting process it may be rapidly moved into its closed position by the entry of a pneumatic or hydraulic pressure medium (as a valve control medium) into the cylinder region 23, in which position it is located a distance 5 (some 0.2 to 0.3 mm) inside the end of the cylinder bore 17 (FIG. 3).

The front face of the head 6 of the valve piston 5 which is located in the area of the valve inlet 16 is shaped in such a way that its radially outer edge protrudes obliquely away from the direction of closure of the valve piston 5 (rounded surface 24 in FIG. 3). This oblique protrusion of the edge of the front face of the piston is formed by an annular recess 25 in the front face of the head 6 so that the sealing flange 26 of the piston head 6 has its smallest cross-section at or near its foot 27. The dimensions of this cross-section are such that when pressure from casting material acts on the front face of the head 6, the peripheral edge 28 of the sealing flange 26 is pressed (accompanied by bending in the region of its narrowest cross-section,27)'

against the wall of the cylinder bore 17 to provide sealing. It is at this point that the action of the casting material pressure effects absolutely reliable sealing of the valve piston relative to the cylinder bore despite the slight play which is otherwise present and necessary to allow the valve piston to move in the bore, which means that no casting material may enter between the piston head and the wall of the cylinder bore and pass into the valve cylinder.

In order to facilitate entry of the sealing flange 26 into the bore 17, its peripheral wall is slightly tapered in the axial direction of closure of the piston so that its inner edge 29 is spaced from the cylinder bore 17 by a greater distance than the outer edge 28.

As the liquid casting material may heat the sealing flange 26 of the piston head 6 (more than it does the valve cylinder 3) the sealing flange will also be for this reason pressed against the wall of the cylinder bore 17. Since the opening of the casting mold generally takes place when the casting material and valve piston are still hot, the valve can only be re-opened by a substantial ejection force, this being applied in the example shown in FIGS. 1 and 2 by the compression springs which have been subjected to pronounced initial stress. When the valve is open the valve head may cool off again to a certain extent, i.e., there is an equalization of temperature with the result that in the next casting process the valve can once again be easily closed.

FIG. 4 shows the valve piston 5 in the closed position, but in the case of an embodiment which varies from that according to FIGS. 1 and 2 in respect to the depth of blind bore 22 in the nut 11. The depth of the blind bore here is so great that the valve head 6 may enter the cylinder bore 17 further than is necessary to close the ventilation duct 4. As a result of this the kinetic energy of the casting material, which is flowing in the ventilation duct and is suddenly braked when the ventilation duct is closed, may be damped in the additional braking zone thus created, in order to avoid the extremely high pressure peaks which are produced when the casting material is suddenly braked or at least to keep them within acceptable limits.

The ventilation valve described above has proven itself under extremely rigid conditions over a satisfactorily long test period and can considerably increase the economics of manufacturing of castings as a result of the elimination of one of the constant sources of disruption.

More than one ventilation valve may also be provided for the ventilation duct. Thus, for example, one valve may be provided in the half 1 of the mold, the other valve laying opposite this in the half 2 of the mold. It is also possible to connect a shock absorber to the ventilation duct next to the ventilation valve, this shock absorber having the same valve design with displacement member and back-pressure element as the ventilation valve described above.

What we claim is:

l. A ventilation valve for closing a ventilation duct in a casting mold, the valve comprising a valve cylinder;

a valve piston slidingly received by the valve cylinder so as to be movable between an open and a closed position in a direction perpendicular with respect to said ventilation duct, said valve closing in the direction of the pressure exerted by casting material onto the surface of said piston which faces said ventilation duct, a displacement member which urges the piston into its open position when the mold is open; and means actuated by closure of themold to move the displacement member away from the piston so that the piston can be brought to its closed position without being hindered by the displacement member load.

2. A ventilation valve as claimed in claim 1, in which the displacement member is spring-loaded towards the direction of the valve piston.

3. A ventilation valve as claimed in claim 1, in which said means to move the displacement member comprises at least one slidable member, one end of which bears against the displacement member and the other end of which projects from the valve body so as to be engageable with part of the mold during closure to move the displacement member.

4. A ventilation valve as claimed in claim 3, including a piston plate on the valve piston arranged to allow actuation of the piston by a hydraulic or pneumatic pressure medium, the slidable member passing slidably through the plate.

5. A ventilation valve as claimed in claim 4, in which the end of the slidable member which bears against the displacement member is provided with a stop interposed between the piston plate and the displacement member.

6. A ventilation valve as claimed in claim 1, in which the displacement member comprises a plate which is axially displaceable in the valve cylinder behind the valve piston, the plate supporting at the side remote from the valve piston a coaxial guide shaft which slides in a guiding bore.

7. A ventilation valve as claimed in claim 6, in which the guiding bore is a blind bore substantially deeper than the length of the piston stroke necessary to close the valve. I

8. A ventilation valve as claimed in claim 1, in which the displacement member is urged towards the piston by a compression spring.

9. A ventilation valve as claimed in claim 8, in which the compression spring abuts against a bolt which is screwed into the valve cylinder.

10. A ventilation valve as claimed in claim 1, in which the valve piston is a plunger piston with a sealing piston head and, when housed in a valve cylinder without a valve seat, closes exclusively by means of plungmg.

II. A ventilation valve as claimed in claim 10, in which upon closure of the valve piston with its sealing piston head enters the valve cylinder to such an extent that its front face, which is to be acted on by casting material is located just inside the valve cylinder bore.

12. A ventilation valve as claimed in claim 10, in which the front face of the piston head is inclined radially outwardly in opposition to the casting pressure.

13. A ventilation valve as claimed in claim 12, in which the front face of the piston head has curved recesses.

14. A ventilation valve as claimed in claim 12, in which the radially projecting part of the piston head is resiliently flexible so that it may be pressed against the wall of the valve cylinder by means of the pressure of the casting material acting on the front face of the piston head.

15. A ventilation valve as claimed in claim 10, in which the peripheral wall of the radially projecting part of the piston head tapers in the closure direction of the axis of the piston.

16. A ventilation valve as claimed in claim 1, in which the part of the mold lying opposite the valve has in the region of the plane of separation a recess which lies opposite the inlet aperture of the valve into which the ventilation duct discharges and which has a greater to move the displacement member. 

1. A ventilation valve for closing a ventilation duct in a casting mold, the valve comprising a valve cylinder; a valve piston slidingly received by the valve cylinder so as to be movable between an open and a closed position in a direction perpendicular with respect to said ventilation duct, said valve closing in the direction of the pressure exerted by casting material onto the surface of said piston which faces said ventilation duct, a displacement member which urges the piston into its open position when the mold is open; and means actuated by closure of the mold to move the displacement member away from the piston so that the piston can be brought to its closed position without being hindered by the displacement member load.
 2. A ventilation valve as claimed in claim 1, in which the displacement member is spring-loaded towards the direction of the valve piston.
 3. A ventilation valve as claimed in claim 1, in which said means to Move the displacement member comprises at least one slidable member, one end of which bears against the displacement member and the other end of which projects from the valve body so as to be engageable with part of the mold during closure to move the displacement member.
 4. A ventilation valve as claimed in claim 3, including a piston plate on the valve piston arranged to allow actuation of the piston by a hydraulic or pneumatic pressure medium, the slidable member passing slidably through the plate.
 5. A ventilation valve as claimed in claim 4, in which the end of the slidable member which bears against the displacement member is provided with a stop interposed between the piston plate and the displacement member.
 6. A ventilation valve as claimed in claim 1, in which the displacement member comprises a plate which is axially displaceable in the valve cylinder behind the valve piston, the plate supporting at the side remote from the valve piston a coaxial guide shaft which slides in a guiding bore.
 7. A ventilation valve as claimed in claim 6, in which the guiding bore is a blind bore substantially deeper than the length of the piston stroke necessary to close the valve.
 8. A ventilation valve as claimed in claim 1, in which the displacement member is urged towards the piston by a compression spring.
 9. A ventilation valve as claimed in claim 8, in which the compression spring abuts against a bolt which is screwed into the valve cylinder.
 10. A ventilation valve as claimed in claim 1, in which the valve piston is a plunger piston with a sealing piston head and, when housed in a valve cylinder without a valve seat, closes exclusively by means of plunging.
 11. A ventilation valve as claimed in claim 10, in which upon closure of the valve piston with its sealing piston head enters the valve cylinder to such an extent that its front face, which is to be acted on by casting material is located just inside the valve cylinder bore.
 12. A ventilation valve as claimed in claim 10, in which the front face of the piston head is inclined radially outwardly in opposition to the casting pressure.
 13. A ventilation valve as claimed in claim 12, in which the front face of the piston head has curved recesses.
 14. A ventilation valve as claimed in claim 12, in which the radially projecting part of the piston head is resiliently flexible so that it may be pressed against the wall of the valve cylinder by means of the pressure of the casting material acting on the front face of the piston head.
 15. A ventilation valve as claimed in claim 10, in which the peripheral wall of the radially projecting part of the piston head tapers in the closure direction of the axis of the piston.
 16. A ventilation valve as claimed in claim 1, in which the part of the mold lying opposite the valve has in the region of the plane of separation a recess which lies opposite the inlet aperture of the valve into which the ventilation duct discharges and which has a greater cross-section than the valve inlet aperture, so that this part of the mold, when the mold is closed does not press directly against the edge of the valve inlet aperture.
 17. A ventilation valve as claimed in claim 2, in which said means to move the displacement member comprises at least one slidable member, one end of which bears against the displacement member and the other end of which projects from the valve body so as to be engageable with part of the mold during closure to move the displacement member. 